Household laundry washing machine with improved spinning phase

ABSTRACT

Washing machine comprising a rotating drum, an electric motor apt to put the drum into rotation, measurement means of the drum rotational speed, means able to detect the torque provided by said motor, computing and control means able to determine and control the instantaneous speed of the drum, wherein, before of the spinning phase, said computing and control means activates the machine into rotation at a predefined speed (Wmain) with the laundry retained on the drum inner wall, compute the static unbalance (m) and the elevation moment (Mel), check if both the following conditions are met: the static unbalance mass (m) is less than a pre-determined value and the absolute value of the elevation moment is less of a predetermined value; if at least one of the unbalancing mass values, or one of the values of said elevation momentum (Mel) are higher than a predetermined respective values, said computing means calculate the difference between the value of said unbalancing mass and the respective said predetermined maximum value, and if said difference is higher than a predetermined limit, said computing and control means will command a predermined speed increase; if not, they command a predetermined speed reduction.

The present invention relates to a laundry washing or to a laundrywashing-dryer machine provided with means able to detect the unbalancemass and to balance the laundry load before the spinning phase. It iswell known during an operating program of laundry washing/drying machineto have one or more spinning phases, i.e. drum rotation phases at muchhigher speed than normally foreseen during the actual washing phases.—

A basic element concerning said spinning phases is the risk of having anunbalanced laundry load with the clothes arranged unevenly inside themachine drum, i.e. accumulated in some definite areas and not availablein other areas, so that during high speed rotation of the drum thisunbalanced load condition may in fact cause remarkable oscillations oreven the risk of a mechanical failure.—

To this purpose the presently available washing machines (orwashing-dryer machine) are provided with special control systems andmethods to check whether the laundry load is evenly distributed orbalanced inside the drum before the execution of the spinning phase,whereas in case of an unbalanced load the control system will remove theunbalance condition and provide for a new distribution phase or at leastbring its amount back to acceptable limits to the machine structure.—

The techniques to achieve this goal are mainly based on measuring thevariation of the drum speed during the starting time of the spinningphase, and on correlating said speed variation to the unbalance level.—

Indeed in a drum with an unbalanced load, moving at a constant rotationspeed, the presence of an unbalanced load causes an increase in the drumspeed in the time interval when the load is in the descending phase, andcauses it to slow down when it is in the ascending phase.

As a result the drum speed takes an oscillatory behaviour around anaverage speed, well known to the man skilled in the art, and that forthe sake of brevity is no further described.

According to the prior art, as in the exemplary patents EP 1342826, EP0335790B1 and FR 2577949, such an oscillatory speed behaviour is thendetected, processed and used in order to generate some procedures ofdrum rotation aimed to avoid or reduce the detected unbalance mass.—

However said solution shows some drawbacks mainly based on the fact thatthe inertia moment of the loaded drum is not detected and then notconsidered in the processing and balancing procedure.—

The inertia moment is however most important as it is well known that itdirectly affects the drum oscillation during the spinning phase; indeedin a drum having an unbalanced load, if the overall drum inertia isincreased, i.e. if the laundry load is increased, the resultingoscillation during the spinning phase is reduced accordingly.—

And on the contrary, if the inertia moment is reduced, that is if thelaundry load is partly removed from the drum, maintaining the initialunbalance mass, then the speed oscillation increases.—

Therefore some specific conditions can come true, wherein during thespinning phase the drum is subjected to an excessive oscillations thatare prejudicial to the machine safety, even if an acceptable unbalancemass still exists.—

A further method to control the unbalance mass is to directly measurethe same unbalance mass, i.e. to measure the vibrations of the washinggroup by using one o more accelerometers.—

Based on the measured values, a procedure is started which is aimed toredistribute the load according to known methods.—

However this solution requires a not negligible computing power,expensive additional sensors, and moreover the unbalance mass evaluationcan be done, with adequate confidence, only when the drum speed is sohigh that the laundry load is retained on the drum inner surface.—

Largely known in the art is a different technique of controlling withinproper limits the drum unbalance mass, and consisting in directlycounterbalancing said unbalance mass; said technique is implemented byusing adequate and generally circular conduits placed solidly with thedrum and that are coaxial with it, and that contain some rotating orfloating masses, typically water, or oil, or rollers or spheres; saidmasses are made to rotate by the drum rotation and soon they tend todistribute themselves in their own accord in a respective position ableto at least partially balance the unbalance mass of the laundry loadcontained in the drum.

Said solutions are exemplified in the European patent appl. n.96114328.6, in WO 93/23687 and also in the patents therein cited.

Said solutions of automatic re-balancing have shown effective from afunctional point of view, but also burdensome and complicated in theconstruction, and furthermore they are also degrading the performancesas the annular chambers, containing the balancing masses, take up a roomthat otherwise could have be taken by the laundry articles.

It would therefore be desirable, and is actually a main purpose of thepresent invention, to provide a clothes washing or washing-dryingmachine that will eliminate, or at least reduce the drawback of theunbalance mass produced by the uneven laundry distribution inside thedrum during the spinning phases at high speed, considering also theactual inertia of the arm containing the laundry load.—

According to a further purpose of the present invention this clotheswashing machine (or washing-dryer machine) shall be able to be easymanufactured by using existing, ready available materials andtechniques, and be competitive in its construction without suffering anyalteration or reduction in the performance and reliability thereof.

These aims are reached in a washing machine (or in a washing-dryermachine) incorporating the characteristics as recited in the appendedclaims and including such operating modes as described below by mere wayof non-limiting example with reference to the accompanying figures, inwhich:

FIG. 1 is a simplified flow-chart of the basic operations and logicalchecks in a washing machine (or washing-dryer machine) according to theinvention.

FIG. 2 is a complete flow-chart of the basic operations and logicalchecks in a washing machine (or washing-dryer machine) according to theinvention.

FIG. 3 is a diagram of a number of electrical signals representingvarious parameters in a washing machine (or washing-dryer machine)working according to the flow chart of FIG. 2.—

GENERAL PRINCIPLES

The requirements of the distribution strategy according to the instantinvention are now generally described, and the description of theoperating modes and of the computations, aimed to define the neededparameters, are deferred further on.—

In order to obtain a good balance of the laundry load it is needed:

-   -   to measure its unbalance mass, and,    -   to find out the best distribution strategy.—

As well known, the unbalance mass can be calculated from the staticlaundry unbalance mass; said static unbalance mass can be measured bymaking an energy balance on an integer number of drum turns.—

Therefore an initial measurement of the inertia moment of the total drum(comprising drum, the whole laundry load and the motor), and thecontinuous measurements (i.e. lasting for the whole time interval of thedistribution process) of the angular drum speed and of the motor torquehave to be carried out.

In order to obtain a good balance of the laundry load it is needed tofind out the best distribution strategy according to the unbalance mass,which of course can be varying during the spinning starting phase;moreover the said distribution strategy has to be able of automaticallychanging itself according to the changing of the unbalance mass.—

The laundry movement inside the drum is random, not foreseeable and inthe facts not controllable from the outside; then, if a favourablesituation takes place, it is advisable to try to freeze it as quick aspossible, by increasing the rotation speed.—

From this point of view it is then useful to drive the drum at asuitably high speed, so that the laundry load is fully retained on thedrum inner surface.—

On the other side, with the increase of the rotation speed, the portionof the laundry load not yet retained against the drum inner surfacetends to decrease, and that may prevent the reduction of the unbalancemass in excess with respect to the maximum allowed value for theunbalance mass.—

As a conclusion, the speed control during the laundry distributionprocess has to duly take into account said two clashed elements;practically speaking, the rotational speed must be controlled in such away to be the highest possibly, having taken into account that thepossibility of eliminating the unbalance mass in excess (with respect tothe maximum acceptable unbalance degree) shall not be excluded.—

The requirements of the distribution strategy according to the instantinvention are now explained.

Definitions

The general equilibrium equation with reference to the rotational speedof the drum with the laundry load is:${J_{TOTAL} \cdot \frac{\mathbb{d}\omega}{\mathbb{d}t}} = {{{- {mgR}} \cdot {\cos( {\omega\quad t} )}} + T_{MOTOR} + T_{FRICTION} + T_{ELEVATION}}$wherein the various terms show the respective following meanings:

-   -   J_(TOTAL) is the total inertia of the rotating masses,        comprising the laundry load, the drum and the electric motor,        respect to the drum axis.    -   ω is the drum angular speed.    -   m is the static unbalance mass.    -   dω/dt is the drum angular acceleration.    -   g is the gravity acceleration.

R is the drum radius.

-   -   mgR·cos(ωt) is the resistant moment due to the static unbalance        mass m (it is an oscillatory value).    -   T_(MOTOR) is the torque provided by the electric motor and        measured on the drum axis.    -   T_(FRICTION) is the friction torque measured on the drum axis.    -   T_(ELEVATION) is the torque, measured on the drum axis, needed        to raise the portion of the laundry load that is not yet        retained on the drum inner surface, without the friction effect        and of the inertial effect.

The overall inertia on the drum axis (J_(TOTAL)) must be measured onceand for all at the beginning of the laundry distribution process, as itis a value that is stable, when the laundry humidity is constant.

The friction torque on the drum axis (T_(FRICTION)) takes into accountall the frictions developed by the machine, comprising both the ballbearings and the gear friction, and those related to the laundryrubbing.—

The elevation torque on the drum axis (T_(ELEVATION)) is the resistanttorque due to the laundry not yet retained by the centrifugal force onthe drum inner surface; indeed in its downwards motion the not yetretained laundry doesn't make any resisting torque, as it doesn't dragsthe drum with it, while it makes a restraining torque in its upwardsmotion.

The energy supplied by the motor to raise the laundry is then dispersedby friction in the warping motion of the laundry load (falling impactand rubbing due to the relative motion among the laundry articles). Theelevation torque is then a negative moment, as the friction torque is.

The parameters used in the distributing procedure are the staticunbalance mass (m) and the elevation torque (T_(ELEVATION)).—

They can be obtained by using the given general equation to calculate anenergy balance over an integer number of drum turns. Therefore anintegration of the same equation between an initial angle θ₁ and a finalangle θ₂=θ₁+2πN, has to be calculated, N being an integer number.—

As the resistant torque generated by the static unbalance mass−mgR·cos(ωt) shows a sinusoidal behaviour with respect to the drumrotation angle, then the unbalance mass amount can be estimated by thefollowing equation, valid for any initial angle θ₁:∫_(θ₁)^(θ₁ + 2π)−mgR  cos   θ  𝕕θ = 4mgR

In order to use the main equation that allows the instantaneousdetermination of the amount of the unbalance mass (m) and of theelevation torque (T_(ELEVATION)), it is requested to measure twoparameters: the drum angular speed (ω), and the motor torque(T_(MOTOR)).—

However here it is intended that the relevant amounts are well known, asthey can be easily detectable with known means and procedures; forinstance by using a tachometer generator and measuring the current takenup by the motor, with respect to its phase; therefore their measurementsand processing are no further discussed.—

Distribution Strategy of the Laundry Load

The elevation torque (T_(ELEVATION)) can be referred as the parameter ofthe percentage of the laundry load not retained to the inner wall of thedrum; if said moment is zero, the laundry articles are fully retained onthe drum inner surface, while as much this parameter increases in itsabsolute amount (being it a negative amount) as the laundry load isallowed to move itself.—

By using the correlation between the elevation torque and the mobilitydegree of the laundry load, it is possible to define an advantageous andeffective strategy for the distribution process.—

According to the above considerations, the procedure for starting thespinning phase without suffering an excessive unbalance mass will haveto consider the following observations:

-   -   The laundry motion inside the drum is a random and not        foreseeable movement, and in fact not controllable from the        outside.    -   The only thing that can be done is to wait that a condition of        low unbalance mass takes place.    -   If a favourable condition takes place, it is requested to freeze        it as quick as possible, by increasing the rotation speed.    -   The higher is the rotation speed, the easier is the freezing of        a favourable condition when it takes place.    -   The lower is the rotation speed, the higher is the laundry        mobility degree, i.e. the load percentage not retained in a        substantially fixed position related to the drum.    -   In order that a favourable condition can take place, it is        requested that the laundry can be moved with a basically high        mobility degree, so that the possibility of eliminating the        unbalance mass in excess (with respect to the maximum accepted        unbalance degree) is not preliminarily excluded.—

If all these facts are taken into account, it is concluded that the bestdistribution strategy consists in the adoption of a rotating drum speedduring the whole distribution phase that be the maximum possible speed,however compatible with a laundry mobility degree good enough to allowthe possibility of eliminating the unbalance mass in excess measuredeach time.—

In order to implement such strategy and in order to control properly thetarget speed during the distribution process, the following conditionmust be implemented:m−S<β·|T _(ELEVATION)|

In it, m represents the static unbalance mass measured at the actualtime, while S gives the threshold, i.e. the maximum allowed limit forthe unbalance mass; therefore m−S represents the unbalance mass inexcess that is requested to compensate.

β is a suitably selected constant value.

If the check of the above given condition is positive (the condition istrue), that means that the laundry articles have not been fullydistributed on the drum wall, but a part of them are still “flying”inside it, due to the fact that the drum speed is too low. Therefore alimited increase of the drum speed is activated.—

If the check of the above condition is negative, (the condition is nottrue), that means that the unbalance mass is too high, independently ofthe fact that the laundry articles are or not retained on the drum innerwall. Then a small decrease in the drum speed is activated, in order toseparate a further portion of the laundry load from the drum inner walland to reposition it in a more balanced way.—

The optimum condition, that permits to start the spinning phase with awell balanced load, is implemented when the unbalance mass is low enoughand, in the same time, the elevation torque is close enough to zero,(i.e. when the laundry load appears to be well distributed in the drumand with a left-over mobility close to zero).—

That means that the following two conditions have to come true:$\quad\{ \begin{matrix}{m \leq S} \\{{T_{ELEVATION}} \leq T_{ELEVATION}^{MAX}}\end{matrix} $where T_(ELEVATION) ^(MAX) is the maximum allowable amount for theabsolute value of the elevation torque.

As a matter of facts, the distribution strategy must consist in that thespinning phase is allowed only after two basic conditions areimplemented, i.e.:

-   -   COND 1: the unbalance mass must be less than a maximum        pre-determined value, and it has to be measured just before of        starting the spinning phase, i.e. when:    -   COND 2: the whole laundry load is almost fully distributed on        the drum inner wall, that is the elevation torque is less than a        maximum predefined amount.—

Such strategy can be effectively understood, in the actual case of awashing machine (or a washing-dryer machine) just before the spinningphase, considering the logical flow-chart of FIG. 1, representing in asimplified form the operating sequence of the various logical andcontrol operations in a washing machine (or in a washing-dryer machine)according to the invention.—

In order to simplify and to make easier the understanding of theinvention, said logical flow-chart shows only the working modes of alogical and working kind that are essential to implement the invention;in the real situation however of a washing machine (or a washing-dryermachine) that actually implements the invention, it is needed and usefulto introduce some further operations and logical functions; these aredescribed in FIG. 2 which represents all working operations andfunctions in a washing machine for actual use.

In the flow-chart of FIG. 1 each block is identified by a specificnumber, that is used in the following description in order to describethe operation modes of the respective blocks:

-   -   Block 1. The spinning phase is started; in said phase the motor        is activated so that it speeds-up the drum speed till to a        pre-determined speed.    -   Block 2. Said pre-determined speed ω_(MAIN) is reached; said        speed is the minimum speed when the laundry load is wholly        distributed on the drum inner surface; usually said speed is        around 110 rpm.    -   Block 3. The measurement of the inertia moment J_(TOTAL) of the        drum, comprised of the laundry load, is done; the measurement of        said value can be easily calculated with known means and        procedures, for instance by the detection of the torque and of        the drum angular acceleration; as these operations are well        known in the prior art, they are not further explained.—    -   Block 4. The average friction torque on one turn (T_(FRICTION))        in the condition where the laundry load is retained on the drum        inner surface is measured; it corresponds (but the sign) to the        average torque supplied by the motor and needed to exceed the        friction in condition of stable target speed, the laundry being        retained by the drum.    -   Block 5. The unbalance mass m and the elevation torque        T_(ELEVATION) are calculated; the two parameters are now        calculated at the actual speed that usually is different from        the speed in the previous block 4, as the latter speed has been        modified by the loop comprising the block 11 described further        on, wherein the actual speed has been accelerated or decelerated        by a limited amount.—    -   Block 6. In this block the test is done whether the unbalance        mass m is less than a predefined value S; if such test is        confirmed, the operation goes on to the following step in the        block 7; said first check is a basic step, as it implements the        first of the two conditions seen above (COND 1).    -   Block 7. In this logical block the test is done whether the        module of the elevation torque T_(ELEVATION) is less than a        maximum specified value T_(ELEVATION) ^(MAX); this second test        implements the second condition given above (COND 2).—    -   Block 8. If said second condition too is confirmed, the spinning        phase is started without further tests, measures and/or        calculations, as the two conditions required of a small and        acceptable unbalance mass, combined with a fairly even        distribution of the laundry load on the drum inner surface, are        accomplished.    -   Block 9. If, on the contrary, in the logical block 6 the        unbalance mass m is not less than the specified limit value S,        or if at the logical block 7 the elevation torque T_(ELEVATION)        is not less than the respective specified maximum value, that        means that at least one of the two main conditions (COND 1, or        COND 2) are not met; therefore it is needed to work out the        logical operation of checking whether m−S<β·|T_(ELEVATION)|,        wherein β is a properly defined constant. If such test is met,        it means that the laundry is not completely distributed on the        drum inner surface, but is still “flying” into it, obviously due        to the fact that the drum speed is too low. In order to overcome        such problem the operation goes on to the following block 10.    -   Block 10. In said block a small step-up of a predetermined        amount is actuated on the drum speed, of course in order to make        the laundry to better adhere to the drum inner surface.    -   Block 11. After the drum speed variations, the routine of the        calculations and of the related tests, previously described in        the logical block 5 on, is initiated until the condition in        block 7 is met, so that it is now possible to start the spinning        phase.    -   Block 12. If in the previous block 9 the given condition is not        met, that means that the unbalance mass is excessive,        independently of the fact that the laundry load is or not        adhering to the drum inner surface; in order to overcome such        constraint, a reduction of a predetermined amount is activated        on the drum speed, to allow that the load into the drum is        separated and is re-distributed in a more even way; of course        that can be not obtained in the first attempt, but this result        can be easily attained with a sequence of different attempts at        progressively lower speeds, as activated by the logical loop        going from the block 11 towards the block 5.—

The flow-chart of FIG. 1 is effective to illustrate the logical andfunctional ground of the invention; however in an actual washing machine(or washing-dryer machine), intended for a real household use, it isneeded to introduce in the working process a number of further checks inorder to make it safer and that in any case determine some limit values,beyond which the washing cycle is stopped in any case.—

With reference to FIG. 2, a second flow chart is showed which comprisesthe flow chart of FIG. 1, but it introduces some new logical andoperating blocks.—

The blocks of FIG. 2 having the same functions of the blocks of FIG. 1are here numbered with the same numbers from 1 to 11; the new blocks arehere numbered from 21 to 29 (however some numbers are missing).—

Moreover the new blocks are easily recognized as their externalperimeter is highlighted with a double line.—

Now the meanings of the main blocks that have been added is explainedshortly, as the reasons of their presence and the related working modesis easily guessed and understood by the man skilled in the art.—

-   -   Block 21. After the checks in the previous blocks 6 and 7, this        operation assures the restoring of the speed condition that is        the same as in the block 2, i.e. wherein the laundry load is        fully distributed on the inner drum wall; it is a mandatory        condition for the spinning phase.—    -   Block 29. t<t_(M): it means that each time the recalculation        loop addresses back to block 5, a check of the operating mode is        done to verify that the total execution of the program is not        longer than a maximum pre-defined time interval; as a matter of        fact it can happen that, observing FIG. 1, the washing machine        (or washing-dryer machine) is never launched into spinning but        it goes on working endless according to the closed loop        5-6-9-10, or 12-11-5.—    -   Block 27 and 27A. ω≦ω_(MINd): it means that, should the speed        attained by the foreseen deceleration be lower than a minimum        pre-defined limit, then the reestablishment to said minimum        speed ω_(MINd) is determined.—    -   Block 28 and 28A. ω≦ω_(MAXd): it means that, should the speed        attained by the foreseen deceleration be higher than a maximum        pre-defined limit, then the reestablishment to said maximum        speed ω_(MAXd) is determined.—    -   Block 23. It is checked whether the drum speed is the same drum        speed ω_(MAIN) in block 2; it is used as a preparatory phase of        the spanning phase, and in this phase the drum speed must be        such to allow the complete distribution of the laundry load on        the inner drum wall.—    -   Block 24. This block too is a check phase before spinning; it is        verified that in the preliminary phase the unbalance mass be low        enough. It can be considered a repetition of the verification of        block 6, but as a matter of facts the latter is an absolutely        needed check to implement the instant invention, as the check in        block 24 is an operation intended to increase the confidence for        a correct operation. There is no need to check here that the        amount of the elevation torque be low enough as, at the present        speed, the laundry load is practically retained by the drum        wall.    -   Block 25. It is a counting register; it counts number of times        the check in block 24 has given a consent for spinning. As to        the sampling frequency of the measurements, and so of the checks        done, it may advantageously be around 50 times/sec. If said        checks are performed for instance N=10 times as represented, it        turns out that only 0.2 seconds are requested to verify, with a        reliable number of times, that all the given conditions, i.e.        the load balance, the laundry distribution and the drum speed        are suitable to start the drum into spinning.—

With reference to FIG. 3, the behaviour of the various parametersmeasured and calculated in an actual working cycle can be observed; ithas to be precisely noticed that the drum actual speed follows veryclosely the target speed, that to its turn shows a saw-tooth profile,being the speed determined by the cited iterative process ofacceleration/deceleration that is continuously implemented and updated(within maximum time limits that have been already explained), accordingto what determined in the blocks 10 and 12.—

It is then apparent that the instantaneous speed basically follows theprogress of said target speed, as it is the latter which controls thetime by time motor working.

Moreover it is to be noticed that at a certain time, T in the diagram,the actual speed tends to increase beyond its previous average amounts;in the facts at this time the spinning phase is started, as the twoconditions 1 and 2, previously described, have been met.

It can be immediately verified that, at that time, the unbalance mass mtakes its minimum amount and, in the same time, the elevation torquetakes its minimum amount, in its absolute value.—

1. Washing or washing-drying machine comprising: a rotating drum, anelectric motor apt to put the drum into rotation, measurement means ofthe drum rotational speed, means able to detect the torque provided bysaid motor, computing and control means able to determine and controlthe instantaneous speed, characterized in that, before of beginning thespinning phase, said computing and control means: do make themeasurement of the total drum inertia (J_(TOTAL)), activate the machineinto rotation at a predefined speed Ω_(MAIN) (2) corresponding to acomplete laundry distribution retained on the drum inner cylindricalsurface, compute the static unbalance mass (m) and the elevation torque(T_(ELEVATION)).
 2. Washing machine according to claim 1, characterizedin that, after having performed the operation of claim 1, said computingand control means determine a working mode according to which theyactivate the spinning phase if both of the following conditions are met:the static unbalance mass (m) is less than a pre-determined value (S)(6), and the absolute value of the elevation torque is less than apredetermined value (T_(ELEVATION) ^(MAX)) (7), said unbalance mass andsaid elevation torque being calculated according to the drum totalinertia, and said conditions being checked also in times not successiveto said calculations.
 3. Machine according to claim 2, characterized inthat, is at least one of the unbalance mass values (m), on or more ofthe absolute values of the elevation torque (T_(ELEVATION)) are higherthan the respective predetermined values, (S, T_(ELEVATION)), saidcomputing means calculate the difference between the value of saidunbalance mass (m) and the respective said predetermined maximum Value(S), and if said difference is less than a predetermined limit(β·|T_(ELEVATION)|) (9), said computing and control means will command apredetermined speed increase (10).
 4. Machine according to claim 2,characterized in that, if at least one of the values of said unbalancemass (m) or of said absolute value of the elevation torque(T_(ELEVATION)) are higher of a respective pre-defined value, saidcomputing means calculate the difference between the value of saidunbalance mass (m) and the respective said maximum predetermined limit(S), and if said difference is higher than a predetermined limit(β·|T_(ELEVATION)|) said computing and control means will command to thedrum a predetermined speed reduction (12).
 5. Machine according to claim3 or 4, characterized in that, after having achieved said predeterminedspeed increase or decrease, said computing means check whether theresulting speed is comprised into a pre-defined interval(Ω_(MINd)÷Ω_(MAZd) (27, 28) and if such condition is positively met, afurther comparison is made (29) whether the working time from thebeginning of the operation as per claim 1 is less than a predefinedmaximum time interval t_(M), and if such condition is met the machineoperation is brought to the beginning of claim 2 (5).
 6. Machineaccording to claim 3 or 4, characterized in that of the resulting speedis outside of a predefined speed interval (Ω_(MINd)÷Ω_(MAZd)), saidcomputing and control mans activate the drum to rotate at a predefinedspeed (Ω_(MINd) or Ω_(MAZd)) (27B, 28B) and after that a furthercomparison is made (29) whether the working time from the beginning ofthe operation as per claim 1 is less than a predefined maximum timeinterval (t_(M)), and if such condition is met the machine operation isbrought to the beginning of claim
 2. 7. Machine according to claim 1,characterized in that said computing and control means are able toperform the following operation: before of commanding the spinningphase, they command the drum speed (21) to the predetermined speed(Ω_(MAIN)) as in claim 1, and then the machine operation is brought tothe beginning of claim
 2. 8.
 8. Machine according to claim 7,characterized in that, after having determined the drum speed, it isable of check that: the drum speed is the same of said predeterminedspeed (Ω_(MAIN), 23), and said unbalance mass (m) is less of apredetermined value (S; 24), and if said check gives a positive result,it increments the number of said operations in a specific addingregister (25), and if the actual number in said register is the same ofa predetermined number (N, 26), then said computing and control meanscommand the spinning phase.—